Method of making an interposer with contact structures

ABSTRACT

A method of making an interposer having an array of contact structures for making temporary electrical contact with the leads of a chip package. The contact structures may make contact with the leads substantially as close as desired to the body of the chip package. Moreover, the contact structures can be adapted for making contact with leads having a very fine pitch. In a first embodiment, the contact structures include raised members formed over a body of the interposer. A conductive layer is formed over each of the raised members to provide a contact surface for engaging the leads of the chip package. In another embodiment, the raised members are replaced with depressions formed into the interposer. A conductive layer is formed on an inside surface of each depression to provide a contact surface for engaging the leads of the chip package. Moreover, any combination of raised members and depressions may be used.

[0001] This application is a divisional of U.S. patent application Ser.No. 09/631,253 filed on Aug. 2, 2000, which is a divisional of U.S.patent application Ser. No. 09/058,586, filed on Apr. 10, 1998, whichare incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. The Field of the Invention

[0003] The present invention relates to structures for electricallyconnecting an integrated circuit to external circuitry. Moreparticularly, the present invention relates to interposer structureshaving formed thereon a plurality of conductive pillars or recesses thatare adapted to make electrical contact with the leads of an integratedcircuit package.

[0004] 2. The Relevant Technology

[0005] Frequently, after an integrated circuit is manufactured, atesting process is conducted on the integrated circuit by subjecting itto a preselected set of input conditions in order to measure itsresponse or other parameters. Such testing is often conducted on a chippackage that includes an integrated circuit. As used herein, the terms“integrated circuit package” and “chip package” refer to an assemblythat includes an integrated circuit or another semiconductor structurein combination with external and additional structure. The term“semiconductor structure” extends to any device or assembly thatincludes circuitry defined in a semiconductive material, and furtherextends to a chip package that includes semiconductive material. Theexternal and additional structure of a package assembly may be used, forexample, for mounting the semiconductor structure to a printed circuitboard or other external circuitry, for establishing electricalconnection between the semiconductor structure and external circuitry,for improving the ease of handling or transporting the semiconductorstructure, and/or for protecting the semiconductor structure fromenvironmental conditions.

[0006] Many chip packages include a lead frame that extends beyond thebody thereof. The lead frame typically includes an array of electricalleads that extend from the internal circuitry of the integrated circuitto the exterior portion of the chip package where they are exposed tothe surroundings. Testing of an integrated circuit package that includesa lead frame assembly is conventionally conducted by providing temporaryelectrical communication between the leads and testing circuitry. Forexample, such temporary electrical connection may be established byusing a set of probes, pins, sockets, or the like, to contact the leads.The integrated circuit package may be clamped or otherwise secured inposition during the testing operation in order for the leads to remainin electrical contact with the corresponding probes, pins, sockets,etc., of the testing circuitry.

[0007] Regardless of which electrical connection technique is employed,it is desirable to effect a connection that causes as little damage aspossible to the leads. If the temporary connection to contact surfacesdamages the leads, the entire integrated circuit package may be rendereduseless.

[0008] The trend in the semiconductor manufacturing industry is towardssmaller devices and an increase in the number of leads connected to anintegrated circuit package. This has the result of reducing the distancebetween nearest leads on an integrated circuit package. In particular,the pitch of leads, which is defined as the distance betweencorresponding points on nearest adjacent leads, has progressively grownsmaller.

[0009] As the pitch of integrated circuit packages decreases, it becomesever more difficult to effectively and reliably establish temporaryelectrical contact with the leads without damaging the leads. Thedifficulties are compounded in light of the fact that testing isgenerally more reliable when electrical contact is made with leads asnear to the body of the integrated circuit package as possible. Ifcontact is instead made with the leads a relatively large distance fromthe body of the integrated circuit package, the resulting longconductive segments of the leads can generate considerable interferenceand noise which may disrupt the testing procedure.

[0010] Establishing electrical connection with leads near the body ofthe integrated circuit package is further desirable as integratedcircuits operate at ever higher speeds. If electrical connection isestablished at a relatively great distance from the body of a high-speedintegrated circuit package, signals are not able to be received andtransmitted at the proper synchronization or at the proper timing, whichmay cause the integrated circuit to malfunction or the testing procedureto become disrupted.

[0011] It can be easily understood that the factors that encourageelectrical connection to be established relatively near the body of theintegrated circuit package are often in conflict with efforts for makingcontact with conventional fine pitch lead frames. The probes, socketsand the like that have been used in the prior art are often not able toadequately balance these considerations and increasingly are unable toprovide reliable electrical connection for conducting testingprocedures.

[0012] Accordingly, it can be appreciated that it would be anadvancement in the art to provide an interconnect structure that canprovide electrical connection with leads near the body of an integratedcircuit package, particularly when the leads have a relatively finepitch.

SUMMARY OF THE INVENTION

[0013] The present invention relates to interposer structures thatinclude a plurality of contact structures formed thereon in a patternthat corresponds to electrical leads of an integrated circuit package.The contact structures are arrayed across a surface of the interposerstructure in a position so as to make electrical connection with theleads of an integrated circuit package when the integrated circuitpackage is positioned thereover. The contact structures include aconductive layer for electrically engaging the leads and an electricaltrace having a first end in contact with the conductive layer and anopposite second end configured to be connected with another conductivestructure. For example, wire bonded leads, conductive tape or non-bondedleads may be connected with the second end of the traces. These wires orleads in turn terminate at terminal contact points that preferably havea pitch greater than the pitch of the leads of the integrated circuitpackage. In this manner, relatively fine pitch leads can be connected toconventional sockets or other mounting structures on a testing devicethat have a greater pitch by means of the interposer structure.

[0014] The interposer structures of the invention include a dielectricor a semiconductor substrate over which the contact structures may beformed. The semiconductor substrate is preferably substantially composedof silicon or a silicon containing material. Alternatively, adielectrics substrate can be formed over a semiconductor substrate. Thedielectric substrate may be disposed over a body portion of theinterposer structure or may instead be an integral portion of theinterposer structure.

[0015] Under a first embodiment of the invention, an array of raisedmembers are formed on the dielectric or semiconductor substrate, witheach raised member having a top surface distal to the dielectric orsemiconductor substrate. A conductive layer is deposited or otherwiseformed on the top surface of each of the raised members. The raisedmembers are sized and spaced so that the conductive layers formedthereover may electrically engage the leads of an integrated circuitpackage. The raised members may be formed from the dielectric orsemiconductor substrate using any suitable etching procedure or othermicromachining operation. Silicon or silicon containing material is apreferred material for use in the dielectric or semiconductor substratebecause such material is relatively easy to pattern to form the raisedmembers, as well as being scalable to relatively smaller geometries andcompared to other materials used in etching procedures or micromachiningoperations.

[0016] Optionally, one or more projecting apex structures are formed intop surface of the raised member, upon which is positioned theconductive layer opposite the top surface of the raised member. Theprojecting apex structures facilitate the establishment of ohmic contactwith the leads by penetrating the surface of the leads, including anyoxide layer that may have been formed thereon.

[0017] According to a second embodiment of the invention, an interposeris provided, wherein the raised members are replaced with an array ofdepressions formed into the dielectric or semiconductor substrate. Aconductive layer is deposited or otherwise formed on an inside surfaceof each of the depressions. The depressions are aligned and spaced sothat the leads of an integrated circuit package may be placed thereinand become electrically engaged with the conductive layers. For example,the depressions may take the form of trenches, each having alongitudinal axis parallel to the longitudinal axis of the correspondinglead. The trenches or other depressions may have one end that is openinto a nest or other low elevation region on the face of the interposerstructure. The nest may facilitate placement of the leads into thedepressions by allowing the integrated circuit package to rest low onthe interposer and near to the plane defined by the array ofdepressions.

[0018] According to either of the foregoing embodiments, electricaltraces preferably extend from the conductive layer along a surface ofthe body of the interposer structure. The traces preferably have acontact pad at one end thereof where a conductive structure such as awire or conductive tape may be attached. Any suitable conductivestructure may be used to electrically connect the trace with externalcircuitry, such as that found in a testing apparatus. For example,conductive tape may be attached to the leads to provide an electricalpath to the testing device. According to a preferred configuration ofthe interposer structure, the conductive tape wraps around an edge ofthe interposer structure and extends to a face of the interposerstructure opposite the contact structures. The conductive tape may endat a terminal contact point that can be connected to a conventionalsocket or probe. Preferably, the terminal contact points on theconductive tape are not aligned across the surface of the interposerstructure, but are instead staggered, thereby increasing the distancebetween adjacent terminal contact points and increasing the pitch.

[0019] When an integrated circuit package is electrically connected tothe interposer structure, the integrated circuit package mayadvantageously be secured thereover in order to reliably establishelectrical connection. This can be accomplished by any of a number ofsuitable methods. For example, a clamping apparatus may be brought intocontact with the leads or with another part of the integrated circuitpackage. The clamping apparatus may be a bar or a plate that is pressedonto the integrated circuit package on the opposite side thereof fromthe interposer structure. Alternatively, a vacuum source may beconnected to a via that extends through the interposer structure andterminates at an end that is adjacent a portion of the body of theintegrated circuit package. Using the vacuum source, the integratedcircuit package may be held onto the interposer structure by differencesin air pressure. In any case, when the interposer structure is used fortesting an integrated circuit, the method of securing the integratedcircuit package onto the interposer structure is preferably temporary.

[0020] According to still another embodiment of the invention, theraised members and depressions of the previous embodiments are replacedwith an array of conductive bumps. The interposer structure of thisembodiment includes a substrate over which a plurality of segments ofconductive tape are positioned. A conductive bump is deposited over eachsegment of conductive tape in order to provide contact surfaces forelectrically engaging the leads of the integrated circuit package.

[0021] In view of the foregoing, the interposer structures of theinvention are able to establish electrical connection to leadsrelatively near the body of an integrated circuit package. This ispossible even in situations where the leads have a very fine pitch.Moreover, reliable temporary electrical contact with leads can beestablished without damaging the leads.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to illustrate the manner in which the above-recited andother advantages of the invention are obtained, a more particulardescription of the invention briefly described above will be rendered byreference to specific embodiments thereof which are illustrated in theappended drawings. Understanding that these drawings depict only typicalembodiments of the invention and are therefore not to be consideredlimiting of its scope, the invention will be described with additionalspecificity and detail through the use of the accompanying drawings inwhich:

[0023]FIG. 1 is a top view of an interposer structure including an arrayof contact structures according to a first embodiment of the invention.

[0024]FIG. 2 is a top view of an integrated circuit package having anarray of electrical leads that correspond to the array of contactstructures of FIG. 1.

[0025]FIG. 3 is a bottom view of the interposer of FIG. 1. An array ofterminal contact points are arranged on segments of conductive tape.

[0026]FIG. 4 is a partial cross-sectional elevation view of anelectrical contact assembly including an integrated circuit packagedisposed over the interposer structure of FIG. 1. An electrical lead ofthe integrated circuit package is placed in electrical communicationwith external circuitry.

[0027]FIG. 5 is a partial cross-sectional elevation view of analternative configuration of an electrical contact assembly.

[0028]FIG. 6 is an exploded perspective view of a replaceable modulethat includes a plurality of contact structures and may be fitted onto asubstrate of an interposer structure.

[0029]FIG. 7 is a perspective view of alternative conductive structuresfor electrically connecting traces with external circuitry.

[0030]FIG. 8 is a perspective view of a contact structure including araised member and a conductive layer having a plurality of projectingapex structures.

[0031]FIG. 9 is a partial perspective view of an interposer structureaccording to a further embodiment of the invention, wherein the contactstructures on the interposer structure include depressions formed into asubstrate.

[0032]FIG. 10 is a partial cross-sectional elevation view of anelectrical contact assembly, including an integrated circuit packageelectrically connected to the interposer structure of FIG. 9.

[0033]FIG. 11 is a cross-sectional elevation view of an interposerstructure having a plurality of contact structures that include bothraised members and depressions.

[0034]FIG. 12 is a partial cross-sectional elevation view of anelectrical contact structure wherein the interposer structure includes asegment of conductive tape and a conductive bump formed on theconductive tape according to another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0035] The present invention relates to interposer structures that maybe used for establishing electrical connection between an integratedcircuit and external circuitry. The interposer structures are useful formaking electrical contact with electrical leads of an integrated circuitpackage relatively near the body of the integrated circuit package. Theinterposer structures include an array of contact structures that aresized and spaced so as to correspond to the leads of the integratedcircuit package. The contact structures may be formed on the interposerwith a pitch small enough to accommodate the leads of substantially anyintegrated circuit.

[0036] The interposers of the invention provide electrical paths fromthe contact structures to terminal contact points that may have a pitchgreater than the pitch of the leads. Accordingly, the interposers may beused to connect an integrated circuit having relatively fine pitch witha conventional socket assembly that has a larger pitch. According to theinvention, the contact structures may take any of a number of forms,including, but not limited to, raised members formed over a substrate,depressions formed into the substrate, conductive bumps formed overconductive tape, and combinations of the foregoing.

[0037]FIG. 1 illustrates an interposer 10 according to the invention.Interposer 10 preferably includes a body 12 on which other portions ofinterposer 10 are formed. Preferably, body 12 is formed by etching amaterial, such as silicon. The etching process stops once body 12assumes a desired shape. Then, a dielectric material is formed thereonso as to isolate, one from another, the discrete conductive componentsare formed by the etching process. Silicon is a preferred material forbody 12 because of the relative ease at which is may be etched orotherwise micromachined. Alternatively, body 12 may be composed of othermaterials, including, but not limited to, ceramics, polymers,composites, and the like. Preferably, body 12 is formed from a materialthat is rigid enough to resist significant bending and deformationduring normal use and that has a coefficient of thermal expansionrelatively close to that of the integrated circuit and the conductivematerial that are to be disposed thereover.

[0038] Preferably, a nest 14 is formed into one face of body 12 as seenin FIG. 1. Nest 14 may be useful for centering an integrated circuitpackage over body 12 and at least partially restraining lateral movementof the integrated circuit package. Nest 14 may take the form of ashallow depression or surface that has a lower elevation than thesurrounding portions of body 12. A plurality of contact structures 16are arrayed over a face of body 12 in order to provide a conductive pathbetween the leads of an integrated circuit package and externalcircuitry. Accordingly, contact structures 16 include a contact surface18 that is positioned to electrically engage leads when the integratedcircuit package is in position over interposer 10. Contact structures 16are positioned over body 12 so as to have a pitch P₁. The pitch of anarray of contact structures is defined herein as the distance between apoint on one contact structure and the corresponding point on thenearest adjacent contact structure.

[0039]FIG. 2 depicts one example of an integrated circuit package 20that may be used in combination with interposer 10 of FIG. 1. Integratedcircuit package 20 includes a body 22 that substantially encases anintegrated circuit assembly such as a semiconductor die. Body 22 isconstructed of, for example, a resin or polymeric material thatinsulates the semiconductor die and protects it from environmentalconditions. Accordingly, the semiconductor die is not visible in FIG. 2.

[0040] The semiconductor die is attached to a lead frame which includesan array of leads 24. The leads 24 emerge from body 22 and are thereforeat least partially exposed to the surroundings. Accordingly, leads 24allow signals or power to be supplied to the internal circuitry of theintegrated circuit. As seen in FIG. 2, the leads have a pitch P₂ that isdefined as the distance between a point on one lead and thecorresponding point on the nearest adjacent lead. It can be understoodthat if the contact surfaces 18 are to be placed in contact with leads24, pitch P₁ of contact structures 16 should be substantially equalpitch P₂ of leads 24. Integrated circuit package 20 has leads 24 thatemerge from body 22 at two of four edges thereof. Other integratedcircuit packages are configured differently, and have leads on as few asone edge or as many as all edges thereof.

[0041] While the embodiments disclosed herein are generally discussed inreference to their use with integrated circuit packages, it should beunderstood that the invention extends to any other chip packages andother semiconductor structures that may be temporarily connected toexternal circuitry. The specific configuration, dimensions, andcomposition of the semiconductor structures and their accompanying leadsare not critical to the invention. Indeed, the interposers of theinvention may be adapted for use with substantially any array of leadsof a chip package or semiconductor structure.

[0042]FIG. 3 illustrates the interposer 10 of FIG. 1 as viewed from theopposite side as the view of FIG. 1. In this embodiment of theinterposer, segments of conductive tape 26 extend from respectivecontact structures 16 seen in FIG. 1, wrap around the edges ofinterposer 10, and terminate on bottom face 28 seen in FIG. 3. Aterminal contact point 30, which is a site that can be connected toconventional sockets, probes, pins, or the like of a testing device orother external circuitry, is formed on each segment of conductive tape26.

[0043] The terminal contact points 30 are preferably arranged in astaggered formation across bottom face 28. One example of a staggeredformation is seen in FIG. 3, and provides that the pitch P₃ of terminalcontact points 30 is greater than pitch P₁ of contact structures 16. Ofcourse, terminal contact points 30 may be arranged on interposer 10according to patterns other than that depicted in FIG. 3. Staggering theterminal contact points across a face of the interposer or at anotherlocation can result in a pitch of the terminal contact points that maybe at least two to three times greater than the pitch of the contactstructures. Another factor that may contribute to the increase in pitchis that the leads 24 may diverge as seen in FIG. 1 as they extend acrossbody 12 and away from contact surfaces 18.

[0044]FIG. 4 depicts an electrical contact assembly in which anintegrated circuit package is electrically connected to externalcircuitry using interposer 10 of FIG. 1. Contact structure 16 is formedover body 12 and includes raised member 32 that extends away from body12. Preferably, raised member 32 is at least partially composed of adielectric material and projects away from body 12 to terminate at a topsurface 34. Accordingly, contact structure 16 is a protruding contactstructure. Raised member 32 preferably includes silicon or a siliconcontaining material and may be formed from the same material as body 12.Indeed, raised member 32 may be integrally formed as a part of body 12.A conductive layer 36 is deposited or otherwise formed over top surface34 of raised member 32. Accordingly, conductive layer 36 is in aposition to electrically engage lead 24 when integrated circuit package20 is positioned over interposer 10.

[0045] Conductive layer 36 includes a conductive material thatpreferably is durable, has good electrical properties, and canrepeatedly make contact with a lead without being significantly worn oreroded. Examples of suitable conductive materials include, but are notlimited to, titanium, titanium silicide, beryllium, copper, tungsten,gold, palladium, and alloys or combinations of the foregoing.

[0046] A trace 38 preferably extends from conductive layer 36 over asurface of body 12 and/or raised member 32. Trace 38 has an end 40 thatis adapted to be connected with a conductive structure such as a wirebonded lead, conductive tape, a non-bonded lead, or the like. Trace 38may comprise the same conductive material as conductive layer 36 and maysimply be an extension of conductive layer 36.

[0047] In the example illustrated in FIG. 4, a segment of conductivetape 26 adheres to end 40 of trace 38. Conductive tape 26 wraps aroundan edge of body 12 and extends to bottom face 28. In this manner, aterminal contact point 30 may be positioned on conductive tape 26 at alocation where it may be connected to a probe 42 or another contact padon testing device 44 or any other compatible contact point on anotherexternal circuitry device. Because conductive tape is conventionallycomposed of a polymeric substrate and a conductive strip formed on oneor both faces thereof, a via 46 or another conductive path may need tobe formed through or around conductive tape 26 to access the conductivestrip.

[0048] In the embodiment of FIG. 4 and other embodiments of theinvention, the conductive structures that provide a conductive pathbetween the leads of the integrated circuit package and externalcircuitry are preferably selected to have matched or uniform impedanceproperties. For example, it is advantageous to use conductive tape 26,traces 38, and conductive layers 36 that have substantially uniformimpedance properties when compared one to another. Matched impedance mayreduce the noise and other interference that may be otherwise producedduring the testing operation, and may further allow reliabletransmission of signals between the testing circuitry and the integratedcircuit, which becomes more important as higher-speed integratedcircuits are used. For the foregoing reasons, conductive tape isparticularly useful in the present invention.

[0049] Using the contact structures 16 of this embodiment and otherembodiments of the invention, electrical connection may be establishedwith leads 24 substantially as near to body 22 as desired. The distancefrom body 22 at which electrical connections are preferably establishedis determined by the properties of integrated circuit package 20 and thedesired results. However, in many cases, contact can be made with leads24 as near as a distance of about 25 microns from body 22 using this orother embodiments of the invention. The dimensional precision of thesilicon substrate can be plus or minus one (1) micron. Preferably, thedetermining factor, however, will be the tolerance and variation of thecorresponding semiconductor package, which is typically plus or minustwo (2) mils (plus or minus fifty (50) microns).

[0050] When an integrated circuit package 20 is disposed over interposer10, there may need to be an apparatus for securing the integratedcircuit package 20 in position. In FIG. 4, this is accomplished by meansof a clamping apparatus 48 that is brought down on lead 24 on a sidethereof opposite conductive layer 36. Alternatively, clamping apparatus48 may be placed in contact with body 22 or one of any number of othermechanisms may be used to secure integrated circuit package 20 inposition. In some cases, adequate electrical contact may be establishedand maintained without the assistance of a clamping apparatus or otherdevice that performs the same function.

[0051]FIG. 5 shows an electrical contact assembly similar to that ofFIG. 4 wherein the terminal contact points 30 are located at a positionseparate from the interposer. In this case, terminal contact points 30are not positioned on bottom face 28 of interposer 10 but are insteadlocated on a distal end of the segment of conductive tape 26. Accordingto the embodiment of FIG. 5, the segments of conductive tape 26 extendaway from body 12. This configuration is best used when leads 24 do notremain coplanar with body 12 but instead curve away therefrom, as seenin FIG. 5. This curvature of leads 24 provides clearance in which thesegments of conductive tape may fan out away from body 12 instead ofbeing wrapped around the edges thereof. The segments of conductive tape26 or other conductive structures connected to traces 38 need not beformed as seen in FIG. 5, but instead may extend in substantially anydirection as desired. In other respects, the electrical contact assemblyof FIG. 5 may be similar to that of FIG. 4. FIG. 5 also illustrates themanner in which raised member 32 may be integrally formed from body 12.

[0052] As seen in FIG. 6, a group of contact structures 16 mayoptionally be formed on an insert module 50, which may be removablyattached to body 12 of an interposer. For example, insert module 50supports a plurality of contact structures 16 that are disposed over asurface thereof. Insert module 50 may be snap fitted, press fitted, orotherwise removably attached to a mating cavity 52 of body 12. Insertmodules 50 may be used so that contact structures 16 may be easilyreplaced when one or more are damaged, instead of having to replace theentire interposer. If insert modules 50 are used with the interposer,one or more insert modules may be used to contact the leads of each edgeof the integrated circuit package.

[0053]FIG. 7 is a partial perspective view of an edge portion of aninterposer structure showing part of several traces 38, and furtherillustrates three examples of methods for electrically connectingconductive structures to traces 38. While three different conductivestructures or conductive members are depicted in FIG. 7, it should beunderstood that generally only one of these three or another suitableconductive structure is selected for any given interposer. However,three alternate methods are presented here for purposes of illustration.

[0054] The first method involves soldering or otherwise permanentlybonding a wire-bonded lead 54 to trace 38. In the second method,conductive tape 26 is attached to trace 38. Conductive tape 26 mayinclude a polymeric substrate 56 which may be a polyimide or othersuitable material coated on one or both sides by a conductive strip 58.For example, conductive tape 26 may be tape automated bonding (TAB) typeconductive tape. Typically, conductive tape 26 is flexible to the extentthat it can be bent and wrapped around corners. The third illustratedmethod involves placing non-bonded lead 60 in contact with trace 38without forming a permanent bond. In general, the foregoing threeexamples of conductive structures are understood by persons of ordinaryskill in the art. Other means for electrically connecting traces 38 withexternal circuitry are certainly within the scope of the invention.

[0055]FIG. 8 is an enlarged view of a preferred contact structure 16. Inparticular, it can be seen that conductive layer 36 is preferablyrelatively thin compared to the dimensions of raised member 32.Optionally, conductive layer 36 will be formed over one or moreprojecting apex structures 62 positioned thereon on a contact surface 64of top surface 34 of raised member 32. Preferably, apex structures 62are first formed in raised member 32, such as when raised member 32 isintegrally formed from body 12, and can be formed by an etching process.Then, conductive layer 36 is evenly deposited over apex structures 62.

[0056] When included in contact structure 16, the projecting apexstructures 62 facilitate the formation of an ohmic contact with a lead.For example, projecting apex structures 62 may slightly cut into theleads and penetrate any oxide layer that might have been formed thereon.A preferred method for forming projecting apex structures 62 isdisclosed in U.S. Pat. No. 5,483,741 issued to Akram et al. which isincorporated herein by reference for purposes of disclosure. Projectingapex structures 62 may also act to securely position an integratedcircuit package in place by at least partially restraining lateralmotion thereof.

[0057] An alternative embodiment of the invention is illustrated in FIG.9 which is a partial perspective view of an edge portion of aninterposer 110. In this embodiment, the contact structures 116 do notinclude raised members, but instead comprise depressions 132 formed intoa substrate by any suitable method. For example, if body 122 consists ofsilicon or a silicon containing material, depressions 132 may be formedtherein by etching or another micromachining operation. Accordingly,contact structures 116 are receding contact structures.

[0058] A conductive layer 136 is preferably formed on an inside surfaceof depression 132. In the embodiment of FIG. 9, this inside surface issubstantially coextensive with the bottom of depression 132. A trace 138preferably extends from conductive layer 136 and has an end 140 that canbe connected with conductive structures or other external circuitry. Thematerials used in conductive layers 136 and traces 138 may be the sameas conductive layers 36 and traces 38 of FIG. 4.

[0059] While a variety of dimensions and configurations of depression132 may be used, the primary factor for their selection is thedimensions of the leads that are to be disposed in depressions 132.Typically, depressions 132 have an end that is adjacent to a nest 114 soas to provide an unobstructed opening by which leads may be disposed indepressions 132.

[0060]FIG. 10 illustrates an electrical contact assembly wherein leads124 of an integrated circuit package 120 are connected to contactstructures 116 of an interposer structure 110. It can be seen thatelectrical contact may be established with leads 124 at a locationthereon as near as desired to body 122 of the integrated circuit package120. As in the previous embodiment, integrated circuit package 120 ispreferably mechanically held in place over interposer 110 such thatelectrical contact with leads 124 is maintained. Securing integratedcircuit package 120 in place may be accomplished by means of a clampingapparatus as depicted in FIG. 4. In this case, a clamping apparatushaving an array of castellations that correspond to depressions 132 mayneed to be used in order to make adequate contact with leads 124.Alternatively, air pressure may be used to hold integrated circuitpackage 120 in place. As seen in FIG. 10, a vacuum via 166 may be formedthrough interposer structure 110 to terminate at a surface of body 122.A vacuum source (not shown) may be connected to vacuum via 166, therebyproducing reduced pressure therein relative to the ambient air pressure.The resulting vacuum holds integrated circuit package 120 in place overinterposer structure 110.

[0061] The embodiment of FIGS. 9 and 10 is especially suitable whenleads 124 are curved so as to be easily placed within a depression 132.However, depressions 132 may be adjusted in order to receive an array ofleads that lie within a plane.

[0062] In order to illustrate a further example of the manner in whichthe contact structures of the invention may be adapted for substantiallyany chip package, FIG. 11 is a partial cross-sectional elevation view ofyet another embodiment of the invention, in which an interposerstructure 210 has an array of contact structures, some of which includeraised members and some of which include depressions. This arrangementmay be used with integrated circuit packages that have two or more setsof leads. For example, some integrated circuits have two lead framesthat lie in planes that are displaced one from another. In this case,depressions 268 engage leads in one plane while raised members 270engage leads in the other plane. In other respects, interposer structure210 may be substantially similar to interposer structures 10 and 110disclosed herein. The raised members and depressions of the inventionmay be adapted as needed to conform to the leads of specific integratedcircuit packages and may be provided in any combination on an interposerstructure.

[0063] Yet another embodiment of the invention is depicted in FIG. 12,wherein the contact structures of the previous embodiments are replacedby conductive tape 326 and conductive bumps 372. Conductive tape 326 maybe disposed on interposer 310 so that it extends from one face ofinterposer 310 to the opposite face. Conductive bump 372 is built upover a conductive strip 358 of conductive tape 326 and provides acontact surface 364 that can electrically engage a lead 324. As in otherembodiments of the invention, conductive bumps 372 are preferablyarrayed over body 322 in a pattern that corresponds to the leads of theparticular integrated circuit package that is used. In other respects,the embodiment of FIG. 12 may be substantially similar to the otherembodiments disclosed herein, in that electrical contact may be madewith a lead substantially as close as desired to the body of anintegrated circuit package. Moreover, reliable contact can be made withan integrated circuit package having a very fine pitch. The pitch ofterminal contact points 330 may be greater than the pitch of the leads324 by staggering terminal contact points 330. The material used inconductive bumps 372 may be the same as the material used in theconductive layers disclosed herein.

[0064] Any of the foregoing embodiments may be adapted for use with avariety of testing practices and methods. One common testing methodalready disclosed herein involves bringing an integrated circuit packageinto contact with the interposers so that testing can be performed.Alternatively, the interposers disclosed herein may be adapted forcontacting integrated circuit packages that are held in a tray oranother similar collection. In particular, the interposers may belowered or positioned onto a stationary integrated circuit package whilethe testing operation is conducted, after which the interposers arelifted away. Still another variation involves providing a hingedassembly including an interposer and an opposable and pivotally attachedclamping apparatus. In this method, the integrated circuit package isplaced on the interposer and within the hinged assembly, while theclamping apparatus is pivoted onto the integrated circuit package. Inview of the foregoing, it should be understood that the interposers maybe adapted for use with substantially any testing practice or method.

[0065] The present invention may be embodied in other specific formswithout departing from its spirit or essential characteristics. Thedescribed embodiments are to be considered in all respects only asillustrative and not restrictive. The scope of the invention is,therefore, indicated by the appended claims rather than by the foregoingdescription. All changes which come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

What is claimed is:
 1. A method for forming an array of contactstructures for providing electrical connection to an integrated circuit,said method comprising: providing a dielectric substrate; forming aplurality of depressions into said dielectric substrate, each of saidplurality of depressions having an inside surface defined thereon; andforming a plurality of conductive layers, one of said plurality ofconductive layers being formed over at least a portion of the insidesurface of each of said plurality of depressions, said plurality ofdepressions being sized and spaced such that said plurality ofconductive layers can be removably and electrically engaged with anarray of electrical leads of said integrated circuit.
 2. The method ofclaim 1, wherein forming said plurality of depressions into saiddielectric substrate comprises conducting an etching operation on saiddielectric substrate.
 3. The method of claim 1, further comprisingestablishing electrical connection between said plurality of conductivelayers and external circuitry.
 4. The method of claim 1, wherein formingsaid plurality of conductive layers comprises forming a layer includinga material selected from the group consisting of titanium, tungsten,beryllium, copper, gold, palladium, combinations thereof, and alloysthereof.
 5. A method for making a contact structure that makeselectrical contact with an electrical lead of an integrated circuitpackage, the method comprising: providing a substrate including adielectric material; forming a depression into said substrate, saiddepression having an inside surface defined thereon; forming aconductive layer disposed over at least a portion of said inside surfaceof said depression, said depression being sized and positioned such thatsaid conductive layer may electrically engage said electrical lead; andforming an electrical trace disposed over a surface of said substrate,said electrical trace being: positioned in electrical contact with saidconductive layer; and composed of a conductive material so as to provideelectrical communication between said conductive layer and externalcircuitry.
 6. The method of claim 5, wherein said substrate comprises asilicon-containing material.
 7. The method of claim 5, furthercomprising making an electrical connection to said electrical trace withconductive tape that extends from said electrical trace to a side ofsaid substrate opposite said surface of said substrate.
 8. The method ofclaim 5, wherein said conductive layer comprises a material selectedfrom the group consisting of titanium, tungsten, beryllium, copper,gold, palladium, combinations thereof, and alloys thereof.
 9. A methodof making an interposer structure for providing electrical communicationbetween an array of electrical leads of an integrated circuit andexternal circuitry, the method comprising: providing a substrateincluding a dielectric material; and forming an array of contactstructures over said substrate, said array of contact structures beingsized and spaced so as to electrically engage said array of electricalleads, each of said contact structures including: a raised memberextending away from said substrate and having a top surface distal tosaid substrate; a conductive layer disposed over at least a portion ofsaid top surface of said raised member; and an electrical trace disposedover a surface of said substrate, said electrical trace being inelectrical contact with said conductive layer, said electrical tracecomprising a conductive material so as to provide electricalcommunication between said conductive layer and said external circuitry.10. The method of claim 9, further comprising forming an array ofterminal contact points in electrical communication with said array ofcontact structures, said array of contact structures having a firstpitch and said array of terminal contact points having a second pitchthat is greater than said first pitch.
 11. The method of claim 10,wherein: said array of terminal contact points is in electricalcommunication with said array of contact structures by conductivemembers selected from the group consisting of conductive tape,wirebonded leads, and non-bonded leads; and said conductive members arepositioned in electrical contact with said electrical traces.
 12. Themethod of claim 11, wherein one or more of said raised members areincluded in a replaceable module that is removably attached to saidsubstrate.
 13. A method of making an interposer structure for providingelectrical communication between an array of electrical leads of anintegrated circuit and external circuitry, the method comprising:providing a substrate including a dielectric material; and forming anarray of contact structures on said substrate, said array of contactstructures being sized and spaced so as to be capable of electricallyengaging said array of electrical leads, wherein each of said contactstructures is formed by: forming a depression into said substrate, saiddepression having an inside surface defined thereon; forming aconductive layer disposed over at least a portion of said inside surfaceof said depression; forming an electrical trace disposed over a surfaceof said substrate; and electrically connecting said electrical tracewith said conductive layer, wherein said electrical trace comprises aconductive material so as to provide electrical communication betweensaid conductive layer and said external circuitry.
 14. The method ofclaim 13, further comprising forming an array of terminal contact pointsin electrical communication with said array of contact structures,wherein: said array of contact structures has a first pitch; and saidarray of terminal contact points has a second pitch that is greater thansaid first pitch.
 15. The method of claim 14, wherein: said array ofterminal contact points is in electrical communication with said arrayof contact structures by conductive members selected from the groupconsisting of conductive tape, wirebonded leads, and non-bonded leads;and said conductive members are positioned in electrical contact withsaid electrical traces.